For those communicating and working by phones, an earphone is a necessary device so that they are unnecessary to hold the handset by one hand since this will make the workers feel inconveniently. In general, the earphone has a battery set as a power supply. However the working period of a battery set is not so long so as to satisfy the requirement of users. In general, the working time period of the battery set is about 2 to 3 hours. Furthermore, it must take time to charge the battery set with a time period. When the power of the battery set approaches to a used up period, the signals from the earphone will become weak and thus the user cannot hear the sound from the earphone clearly. Moreover, in charging the battery set of the earphone, the earphone is placed on a charger for a time period of at least 2 hours. In this time period, the earphone cannot be used. If the battery set is charged frequently, the lifetime of the battery set will reduce so that the earphone having the battery set will be deserted as the exhaustion of the battery set. Thus, in the prior art, the earphone is used as a consuming product, namely, the user must replace the earphone frequently for matching a coupled phone. Thereby the prior art is not only inconveniently, but also is uneconomic.